LAWRENCE (AP) — University of Kansas police are investigating after about 20 used shell casings were found outside the university’s administrative building.

Police say they have found no evidence that a weapon was shot anywhere near Strong Hall before the cases were found Tuesday in bushes. The Lawrence Journal-World reports police believe the person or people who left the shell casings were trying to make a statement but they didn’t elaborate on what type of statement.

A Kansas law that took effect in July required state universities to allow concealed guns on their campuses. There has been strong opposition to the law on many of the universities’ campuses.